Method of lasting leather uppers



March 26, 1968 R. STUBBINGS 3,374,496

METHOD OF LASTING LEATHER UPPERS Filed Nov. 5, 1965 2 Sheets$heet 1 moIZXmwM/re, 0% also drain [Very 00:e

| [lllllll I llllllll] ||||1|| HOURS OFF THE LAST com aor/lson ofvar/bus beaf sel /my lec/m/yues FIG. I

March 26, 1968 R. STUBBINGS METHOD OF LASTING LEATHER UPPERS 2SheetsSheet 2 Filed Nov. 3, 1965 R00 flO/STURE, SHRU/IKEN AT 375). FORVAR/008 TINES,

KJM/N. COOLING, RELEASE.

Jm/n

sec.

l I l l I 2 HOURS RECOVERY w w m FIG. 2

m w w HOURS RECOVERY FIG. 3

INVENTOR.

United States Patent f 3,374,496 METHOD OF LASTING LEATHER UPPERS RobertStubbings, 7721 N. Regent Road, Milwaukee, Wis. 53217 Filed Nov. 3,1965, Ser. No. 506,250 7 Claims. (Cl. 12--145) ABSTRACT OF THEDISCLOSURE Process of shoemaking wherein a leather upper is assembled ona last without substantial stretching so that the upper assumes thegeneral contour of the last, drying the unlasted upper (if not alreadymoisture free when assembled on the last and heating the upper tobetween 250 and 450 F. to shrink the upper and cause it to last itself.

My invention relates to shoemaking and comprises a novel method oflasting leather shoes.

Heretofore it has been almost universal practice to assemble an upper ona last to which an insole has been secured. Then the assembled upper ispulled over the last by machine, the lower margins of the upper beingtacked temporarily to the insole. Subsequently the sides, the toe, andthe heel seat portions of the upper are tightly pulled over the last andtheir overlasted margins permanently secured to the insole.

Relatively recently there have been developments designed to increasethe faithfulness with which the upper conforms to the shape of the lastand to decrease the time the upper must remain on the last in order toretain permanently the desired shape, In general these new developmentsare referred to as heat setting and involve su-bjecting the shoe, whilestill on the last, to heat, with or without added moisture, attemperatures ranging up to about 250 F.

I have discovered that if an upper of relatively dry leather isassembled loosely upon a last and then subjected to a temperaturebetween 250 F. and 450 F., the heat will cause the upper to shrink andactually last itself in a few minutes. Moreover, the shoe so made willretain the shape of the last to a degree not hitherto achieved. The lastcan be removed as soon as the heating step is over, since the leather ofthe upper will have taken a permanent set.

In addition to the marked increase in the quality of the finished shoe,the process of my invention has important economic advantages. Therelatively costly lasting machines can be eliminated, together with manylasting operations requiring highly skilled workers. Hence shoes of thefinest quality can be produced at reduced cost.

Other features of my invention will be more readily understood andappreciated from the following detailed description of a preferredembodiment thereof, selected for purposes of illustration, together withthe accompanying drawings, in which:

FIG. 1 is a graphical representation of the shape retention (set), ofleather uppers given various kinds of treatment,

FIG. 2 is a graphical representation showing the effect of varying thetime of treatment, and

FIG. 3 is a graphical representation showing the effect of differenttemperatures as well as the difference in treating loosely lasted andtightly lasted shoes.

In conventional lasting the leather is stretched from about 15% to 35%in area, as the result of the action of the lasting pincers in grippingand pulling the upper about the last. If such a shoe is then subjectedto moist heat at about 250 F. and then removed from the last, the shoewill retain about 70% to 80% of the shape set. For a discussion of themeasurement techniques I refer to a 3,374,496 Patented Mar. 26, 1968paper by Butlin (I.S.L.T.C., 47, 3, 1963) and my paper in the Januaryissue of the Technical Journal of the National Footwear ManufacturersAssociation, vol. 3, No. 1, p. 23 et seq.

It will first be necessary to define some of the terminology involved. Iuse the term tightly lasted to refer to conventional lasting in thecourse of which the percentage of stretch of a given area of the upperwill be from about 15 to 35 By loosely lasted I mean a lasting processin which a given area of the leather upper will be stretched from zeroto about 10% so that the upper loosely assumes the general contour ofthe last. The determination of the amount of such stretch may mostconveniently be made by employing the grid system disclosed in detail inmy paper cited in the foregoing paragraph. Briefly, a grid pattern of.1" is printed on the flat leather parts of the shoe before they arestitched to form an upper. After the printed upper has been lasted,measurements may be made of the distortion of the pattern caused by thestretching of the leather during the lasting.

In FIG. 1 there is graphically presented the results of experimentsduring which upper leather was subjected to treatment at varioustemperatures, for various times, using leather having differentmoisturecontents. The curves show the loss and percentage set up to hours afterthe last has been removed. It will be seen that the optimum set isachieved when the upper is fairly dry (12% moisture), the stretch iszero, and the upper has been subjected to 375 F. for three minutes. Thenext most favorable result is achieved with an upper having from 12% to30% moisture, loosely lasted and subjected to 375 F. for five or tenminutes. In both examples, the temperature and time are sufficient tocompletely dry the upper so that it is moisture free and thereaftershrink the upper to cause it to last itself. The same figure revealsthat a tightly lasted shoe will not hold its set, regardless of otherconditions of treatment, in any way comparable to the set retentionexhibited by loosely lasted shoes subjected to heat treatment.

FIG. 2 shows graphically the effects produced by varying the duration ofthe heating step from thirty seconds to five minutes and reveals thatthe optimum period is from three to five minutes, provided that theupper is relatively dry to start with.

Other tests show that the shrinkage takes place when the upper has beendried so that its moisture content is approximately 12% to 15%. If anupper having, say, 30% moisture is subjected to a temperature between250 F. and 475 F., it will be found that there is an appreciable periodbefore the shrinkage takes place; during this period the leather losesmoisture until its moisture content has been reduced to from 12% to 15%.As soon as that condition is reached, the shrinkage takes place in lessthan three minutes. If the leather is wringing wet, having a moisturecontent appreciably greater than 35%, the result of treatment at thetemperatures here involved will be to ruin the leather. It is thereforean essential condition for successful operation of the process of myinvention that the leather have a moisture content not greater thanabout 35%.

In FIG. 3 there is a graphic representation of the results of tests madeto determine the effect of varying temperatures, and the curvesdemonstrate that a loosely lasted upper treated at 265 F. for fiveminutes will retain its set very much more faithfully than eithertightly or loosely lasted uppers treated at lower temperatures. Varioustypes of upper leather are available on the market, and there isprobably for each type a threshold temperature below which thephenomenon here utilized will not take place. In general, however, it issafe to use 250 F. as a practical lower limit.

. Of course, if the temperatureis too high, the leather M.

. ommended. It should be stated that the upper limit for the operatingtemperature is governed to some extent by the moisture content of theleather upper being treated.

, If the moisture content is in the neighborhood of 30%, it

is wise to operate at the lower portion of the temperature range; if theleather has a moisture content close to the low end (12% to 15%), thetreatment may be carried out at a temperature approaching the. high endof the margin. 4

I have conducted experiments to determine whether or not it is essentialthat the lasted upper be cooled, after the heat treatment has beencarried out, but the results showed that a cooling step is technicallyunnecessary, although for practical reasons it is desirable that theupper be permitted to cool down approximately to room temperature beforethe last is removed.

Those skilled in the art will immediately understand that the processofmy invention is based on two principles which run counter to commonlyaccepted shoemaking practice. The temperature range. of from 250 F. to450 F. is very much higher than it has been thought safe to employ.Also, it has been almost universal practice to'mull uppers prior tolasting, since an increase in moisture content renders leather easier tolast. In this connection it should be pointed out that in addition toeliminating conventional lasting processes and equipment, the process ofmy invention also eliminates the mulling step.

While it is preferable that the shoe be loosely lasted, the beneficialresults of the process of my invention can be secured by other means.Generally this involves providing means whereby the upper can shrinkback to zero percent area'stretch. For example, a shoe may be lasted inconventional manner, the last removed, and another last inserted, thesecond last being a size smaller than the first last; the re-lasted shoeis then heat shrunk in accordance with my invention. Alternatively, itmight be possible to provide a last fitted with means for reducing itsvolume after lasting and before the heat treatment is utilized.

I have found that the dry heat shrinkage process of my invention in noway adversely affects the qualityof the leather. There is no change inits flexibility, strength, stififness, or grain pattern.

Those skilled in the art will readilyunderstand and out substantialstretching so that the upper assumes the 4 appreciate the manyvariations which may be utilized in carrying out the process of myinvention, the scope of which is measured by the appended claims.

I claim:

1. The process of shoemaking comprising the steps of assembling aleather upper havinga moisture content on a last without substantialstretching so that the upper assumes the general contour of the last,drying the unlasted upper while so assembled on the last by subjectingthe same to heat between 250 and 450 F. for a period of time sufficientto remove substantially all moisture from the upper, and continuing theheating within said temperature range tocause the upper to shrink andlast itself, and thereafter removing the'upper from the last."

2. The process as set forth in claiml wherein the temperature is about375 3. The process as set forth in claim 2 wherein the moisture contentof the upper before it 'is placed on the last is about 12%.. a

4. The process as set forth in claim 3 wherein the overall heatingperiod is about 3 minutes.

5.v The process of shoemaking comprising the steps of assembling amoisture-free leather upper on a last withgeneral contour of the last,subjecting the unlasted upper While so assembled on the last to heat ata temperature between 250 to 450 F. to cause the upper to shrink andlast itself, and thereafter removingthe upper from the last.

6. The processes set forth in claim 5 wherein the temperature is about375 F.

7. The process of shoemaking comprising the steps of assembling aleather upper having a moisture content of about 12% to 30% on a lastwithout substantial stretch ing so that the upper assumes the generalcontour of the last, drying the unlasted upper Whileso assembled on thelast by subjecting the same to heat at about 375 F. for a period of timesufficient to remove substantially all moisture from the upper, andcontinuing the heating at said temperature to cause the upper to shrinkand last itself, the overall heating period being from about 5 to 10minutes, and thereafter removing the upper from the last.

References Cited UNITED STATES PATENTS Re. 25,411 7/1963 Bromfield12-142 2,973,530 3/1961 Bromfield 12 142. 3,176,333 4/1965 Maeser12-.-142 3,237,227 3/1966 Bromfield 12 1 X PATRICK D. LAWSON, PrimaryExaminer.

